The most commonly implemented artificial lift system in the world is sucker rod pumping. A sucker rod pump (also referred to as a pumpjack or beam pump) is a vertically reciprocating piston pump in an oil well that mechanically lifts liquid out of the well. Sucker rod pumps may employ a pumping unit, a gearbox, and a prime mover at the surface, which drives a downhole pump plunger via a sucker rod string that connects them. A non-limiting illustrative example of sucker rod pump is illustrated in FIGS. 1A-1C. The sucker rod string can be made up of sections of steel rods with different diameters or a combination of steel and fiberglass rods with different diameters. When operating a sucker rod pumping system, being able to determine and diagnose the performance of the downhole pump is critical. A dynamometer measures and records the load and position at the polished rod (the rod that is at the top of the sucker rod string, located at the surface) during the stroke of a pumping unit. This data may be plotted on a graph or display that is often called a surface dynagraph card or surface card. The polished rod (surface) load and position data may be used to compute the load and position of the downhole pump. The plot of the load and position data of the downhole pump is called the pump dynagraph card or downhole card.
Sucker rod pumping systems may monitor the data from the pump dynagraph card and make decisions based on the data. Based on the shape of a resulting plot, pump and/or well conditions may be diagnosed, such as full pump, tubing movement, fluid pound, gas interference, etc. (See FIG. 1D). Some methods for diagnosing performance of a sucker rod pumping system utilize finite differences methodology (e.g. U.S. Pat. Nos. 7,168,924 and 7,500,390). These methods can sometimes produce noisy results with respect to the behavior of the rod string and pump. This noisiness is primarily due to the fact that the derivatives that are estimated numerically through finite differences can amplify the noise at each step, leading to inaccurate results. Additionally, some sucker rod pump control systems are characterized as “real-time,” but are not truly real-time systems. In these systems, the data is measured for the duration of the entire pumping cycle (a stroke of the pumping unit) before any calculations are initiated. Once the pumping unit completes the pumping cycle and is beginning the next, such system then begins computing the downhole card and generating the output.
Improved systems and methods for monitoring of downhole pump conditions are discussed herein. These improved systems and methods provide real-time monitoring, high accuracy, and low noise when monitoring downhole pump conditions.